JP4242731B2 - Lens measuring machine - Google Patents

Description

The present invention relates to a technique for measuring the characteristic data of the lens, directed to the lens measuring apparatus for measuring the aperture characteristics particularly with spectral transmittance.

The photographing lens is not completely colorless and transparent, and the material of the lens has a specific color (specific spectral transmittance), and the spectral transmittance changes depending on the coating. Therefore, in an electronic camera, a technique is known in which a lens has necessary information such as spectral transmittance characteristics of a photographing lens, and based on that information, a color image captured by a solid-state imaging device is corrected (for example, Patent Document 1).
Japanese Patent Laid-Open No. 10-39363

  By the way, the lens characteristics include a diaphragm characteristic as well as the above-described spectral transmittance characteristic. This aperture characteristic indicates the relationship between the drive amount of the aperture driving actuator and the aperture value, and has a different value for each lens.

  In general, a solid-state image pickup device such as a CCD has a narrower latitude than a film, and thus it is necessary to accurately control an exposure amount, that is, an aperture value and a shutter time value. Therefore, it is necessary to have information on the above-described aperture characteristics for each lens.

  However, the work of measuring these lens characteristics and incorporating the information into the lens is time-consuming work, and the measurement of these lens characteristics is performed independently. Therefore, in order to improve the efficiency of the camera assembly line, it is necessary to increase the efficiency of the measurement of these lens characteristics and the incorporation of information.

The present invention relates was made in view of the circumstances, and an object thereof is to provide a lens measuring machine capable of efficient measurement and write operations of the lens characteristics (characteristics and aperture spectral transmittance characteristics) .

According to a first aspect of the present invention, there is provided a lens measuring machine comprising: a mount portion for mounting a test lens; a light source that emits a measurement light beam; and an incident through the test lens mounted on the mount portion. Based on the photometric means for measuring the light intensity of each wavelength for the measurement light flux and the measurement light flux incident without passing through the test lens, and the output data of the photometry means in each case Spectral transmittance detection means for detecting the spectral transmittance of the test lens, the output of the photometry means, and the spectral characteristics of other photometry means provided in the camera body to which the test lens is mounted The luminance calculation means for calculating the luminance data from the lens and the diaphragm provided in the lens to be tested mounted on the mount are moved to a plurality of positions including the open position, and the respective positions are set. That on the basis of the luminance data, the effective aperture detection means for detecting the effective aperture value, and data based on the output of the spectral transmittance detection means, throttle position and the effective aperture value based on the output of the effective aperture detecting means Storage control means for storing the corresponding data in a storage means provided in the lens to be examined.

  According to a second aspect of the present invention, there is provided the lens measuring instrument according to the second aspect, wherein the spectral transmittance detecting means is spectral data of the measurement light beam incident through the lens to be tested. Then, a spectral calculation of the spectral data of the measurement light beam incident without passing through the test lens and a normalization calculation for the ratio calculation result are performed to output the spectral transmittance.

  According to a third aspect of the present invention, in the lens measuring machine according to the above-described invention, the effective aperture value detecting means calculates the effective aperture value (AVR) by the following equation.

AVR = AV0−log ₂ {S (P) / S (0)}
AV0: Open aperture value in the design of the test lens S (P): Luminance data at the aperture position P S (0): Luminance data at the open position

  By using the lens measuring device of the present invention, it is possible to improve the efficiency of measuring lens characteristics (spectral transmittance characteristics and aperture characteristics) and writing information thereof.

[Configuration and operation of electronic camera]
Before describing the lens measuring machine according to the embodiment of the present invention, the configuration and operation of an electronic camera will be described. FIG. 1 is a block diagram showing the configuration of the electronic camera.

  The electronic camera includes an interchangeable lens unit 10 and a body unit 30. The interchangeable lens unit 10 is configured to be detachable from the body unit 30 via the lens mount 8 and the body mount 31.

  The interchangeable lens unit 10 includes a photographic lens 11, a lens motor 12, a lens driving mechanism 13, a lens motor driving circuit 14, a photo interrupter 15, an aperture motor 16, an aperture driving mechanism 17, an aperture motor driving circuit 18, an aperture 20, a slice 21, A position detection board 22 and a microprocessor 25 are provided.

  The lens motor 12 is constituted by a DC motor, and moves the position of the photographing lens 11 back and forth via the lens driving mechanism 13. The rotation amount of the lens motor 12 is converted into a pulse signal by a photo interrupter 15 provided on the rotation shaft of the lens motor 12. Further, the reference position of the photographic lens 11 is detected by a circuit constituted by the slice 21 and the position detection board 22.

  The aperture motor 16 is composed of a stepping motor, rotates according to a pulse signal input from the aperture motor drive circuit 18, and controls the opening degree of the aperture 20 via the aperture drive mechanism 17.

  The microprocessor 25 comprehensively controls the interchangeable lens unit 10. That is, a drive signal is output to the lens motor drive circuit 14 and the aperture motor drive circuit 18, a pulse signal indicating the rotation amount of the lens motor 12 is received from the photo interrupter 15, and the position of the imaging lens 11 is detected. Further, the microprocessor 25 exchanges signals with the body unit 30 and receives information for controlling the operation of each part of the interchangeable lens unit 10.

  The body unit 30 includes a quick return mirror 32, a shutter 33, an image sensor 34, an image sensor IF circuit 35, a control unit 36, an image display unit 37, a data recording unit 38, an operation SW 39, a storage device 40, a pentaprism 41, an eyepiece. A lens 42, a photometry circuit 43, a sub mirror 44, an AF sensor 45, a focus detection circuit 46, a shutter drive mechanism 47, and a mirror drive mechanism 48 are provided.

  The quick return mirror 32 guides the subject image to the pentaprism 41 and the AF sensor during the non-shooting operation. The image sensor 34 converts an optical image of a subject into image data that is an electrical signal using, for example, a CCD. The control unit 36 comprehensively controls the operation of the electronic camera and performs various image processing on the image data. Further, the lens characteristic information of the photographing lens 11 is acquired through communication with the microprocessor 25 in the interchangeable lens unit 10.

  The image display unit 37 converts the image data and displays it on a liquid crystal monitor or the like. The data recording unit 38 records image data on a recording medium such as smart media. The operation SW 39 is a SW for the photographer to operate the electronic camera.

  The photometry circuit 43 receives a part of the subject light image from the pentaprism 41 by a photoelectric conversion element (not shown) and measures the luminance. The controller 36 calculates the exposure condition based on this measurement data. The AF sensor 45 receives the subject image divided by the sub mirror 44. The focus detection circuit 46 detects the in-focus state based on the output of the AF sensor 44.

  Next, the operation of the electronic camera will be described.

  When the photographer presses a release button (not shown) from the operation SW 39 by one step, the control unit 36 calculates an aperture value for obtaining an appropriate exposure based on the subject brightness data measured by the photometry circuit 43, The result is transmitted to the microprocessor 25. The microprocessor 25 controls the number of pulses for driving the aperture motor 16 so as to obtain a desired aperture based on the aperture characteristics of the photographing lens 11.

  Further, the control unit 36 transmits a driving signal of the photographing lens 11 for focusing to the microprocessor 25 from the detection result of the focus detection circuit 46. The microprocessor 25 rotates the lens motor 12 via the lens motor drive circuit 14 to move the photographing lens 11 to the in-focus position.

  When the photographer presses a release button (not shown) in two steps from the operation SW 39, the control unit 36 operates the quick return mirror 32 and the shutter 33 to guide the light image of the subject to the image sensor 34 and obtain it from the image sensor 34. Image processing is performed on the obtained image data. At this time, the control unit 36 performs processing such as color correction based on the spectral transmittance characteristics of the imaging lens 11 received in advance from the microprocessor 25.

[Configuration and operation of lens measuring machine]
Next, a lens measuring machine according to an embodiment of the present invention will be described.

  FIG. 2 is a diagram showing the configuration of the lens measuring machine according to the embodiment of the present invention.

  The lens measuring machine includes a lens holding jig 1, a luminance box 2, a spectroscope 3, an optical fiber 4, a CCD interface circuit 5, a personal computer (hereinafter referred to as “PC”) 6, and a communication interface circuit 7.

  The lens holding jig 1 holds the lens exchange unit 10 described above via the lens mount 8. The luminance box 2 stores a light source for measuring lens characteristics. The spectroscope 3 is provided with a slit 3a, a collimate mirror 3b, a diffraction grating 3c, a focus mirror 3d, and a CCD line sensor 3e, and measures the spectral intensity of light guided through the optical fiber 4. The CCD interface circuit 5 delivers the measured spectral intensity to the PC 6. The PC 6 calculates a spectral transmission characteristic based on the measurement value of the spectroscope 3 and transmits information to the interchangeable lens unit 10 via the communication interface 7. Further, the PC 6 calculates a lens aperture characteristic based on the aperture value and the spectral transmission characteristic received from the interchangeable lens unit 10, and transmits the information to the interchangeable lens unit 10 via the communication interface 7.

  Since the configuration of the interchangeable lens unit 10 is the same as that described with reference to FIG. 1, detailed description thereof will be omitted, and the same reference numerals are given to the portions showing the same functions. The microprocessor 25 in the interchangeable lens unit 10 has a function of exchanging signals with the PC 6 and storing lens characteristic data transmitted from the PC 6 in a flash ROM 25a which is an internal storage unit.

  FIG. 3 is a diagram illustrating the configuration of the PC 6.

  The PC 6 includes an input / output control unit 6a, a spectral transmittance detection unit 6b, a luminance calculation unit 6c, an effective aperture value calculation unit 6d, and a storage control unit 6e.

  The input / output control unit 6a is an information interface that exchanges information with the lens measuring machine. The spectral transmittance detector 6 b calculates the spectral transmittance of the photographing lens 11 based on the measurement value of the spectroscope 3. The luminance calculation unit 6 c calculates luminance data based on the measurement value of the spectroscope 3. The effective aperture value calculation unit 6d calculates an effective aperture value from the luminance data and the aperture value of the aperture 20 in the interchangeable lens unit 10. Here, the effective aperture value is not a design value but an aperture characteristic value that the imaging lens 11 actually has. The storage control unit 6 e stores the lens characteristic value in the microprocessor 25 in the interchangeable lens unit 10.

  Next, the operation of the lens measuring machine will be described.

  FIG. 4 is a flowchart showing a general procedure for measuring and incorporating lens characteristics using the lens measuring instrument according to the present embodiment, and FIGS. 5 and 6 are procedures for measuring and incorporating lens characteristics of a PC. FIG. Hereinafter, the operation of the lens measuring machine will be described with reference to FIGS.

  The operator of the camera assembly line activates the spectral transmittance detector 6b in the PC 6 without the lens replacement unit 10 and takes in the spectral sensitivity data of the light source of the luminance box 2 (T100).

  When the measurement of the spectral sensitivity characteristic of the light source is instructed (S200 Yes), the spectral transmittance detector 6b reads the data of the CCD line sensor 3e from the spectroscope 3 (S203), and the data is spectrally transmitted through the photographing lens 11. This is stored as reference spectroscopic data necessary for measuring the rate (S204).

  Next, the operator attaches the interchangeable lens unit 10 to the lens holding jig 1 (T101), activates the spectral transmittance detector 6b in the PC 6, calculates the spectral transmittance, and stores the result in the interchangeable lens unit 10. (T102).

  When the measurement of the spectral transmittance characteristic of the light source is instructed (S201 Yes), the spectral transmittance detector 6b moves the photographing lens to the reference position (S210). That is, an instruction to move the photographing lens to the reference position is output to the microprocessor 25. The microprocessor 25 drives the lens motor 12 to move the photographing lens 11, and stops the movement of the photographing lens 11 when the slice 21 moves to a predetermined position on the position detection substrate 22.

  Then, the spectral transmittance detector 6b sets the aperture to the open position (S211). That is, an instruction to open the diaphragm 20 is output to the microprocessor 25. The microprocessor 25 applies a pulse to the aperture motor 16 to rotate it so that the aperture is fully opened.

  Subsequently, the spectral transmittance detector 6b reads the data of the CCD line sensor 3e from the spectroscope 3 (S212), and calculates the ratio between the data of the CCD line sensor 3e and the reference spectral data stored in step S204. Spectral transmittance is calculated (S213).

  FIG. 7 is a diagram showing the spectral characteristics. In FIG. 7, Ref (n) indicates the spectral characteristic of the light source of the luminance box 2, and Lns (n) indicates the spectral characteristic of the light that has passed through the photographing lens 11. Note that n is a light receiving element number of the CCD line sensor 3e, that is, a value corresponding to the wavelength of light.

FIG. 8 is a diagram showing the spectral transmittance characteristics of the photographing lens. The spectral transmittance T (n) is expressed by the formula (1).
T (n) = Lns (n) / Ref (n) (1)
Then, the spectral transmittance detector 6b converts the spectral transmittance T (n) curve shown in FIG. 8 into the format of the spectral transmittance table. FIG. 9 is a diagram illustrating an example of a spectral transmittance table. In this table, the wavelength increment is 10 nm, and the transmittance is represented by a normalized value (output ratio) in which the maximum value (Tmax) is #FF in Hex display.

  Next, in the PC 6, the storage controller 6e is activated to transmit the calculated spectral transmittance table to the microprocessor 25 and store it in the internal flash ROM 25a (S214).

  Next, the operator activates the luminance calculation unit 6c and the effective aperture value calculation unit 6d in the PC 6, calculates the effective aperture value, and stores the result in the interchangeable lens unit 10 (T103).

  When the measurement of the effective aperture value is instructed (S202 Yes), the luminance calculation unit 6c moves the photographing lens to the reference position (S220). That is, an instruction to move the photographing lens to the reference position is output to the microprocessor 25. The microprocessor 25 drives the lens motor 12 to move the photographing lens 11, and stops the movement of the photographing lens 11 when the slice 21 moves to a predetermined position on the position detection substrate 22.

  Then, the luminance calculation unit 6c sets the aperture to the open position (S221). That is, an instruction to open the diaphragm 20 is output to the microprocessor 25. The microprocessor 25 applies a pulse to the aperture motor 16 to rotate it so that the aperture is fully opened.

  Subsequently, the luminance calculation unit 6c reads the data of the CCD line sensor 3e from the spectroscope 3 (S222), and corrects the data of the CCD line sensor 3e based on the characteristics of the photometric sensor (S223). The photometric sensor is a photoelectric conversion element such as a photodiode installed in the photometric circuit 43 of the electronic camera.

  FIG. 10A is a diagram showing the spectral characteristics and correction curve of the photographic lens. The correction curve α (n) uses the sensitivity characteristic of the photometric sensor. The corrected spectral characteristic LNS (n) is calculated according to equation (2).

LNS (n) = Lns (n) × α (n) Equation (2)
Then, the luminance calculation unit 6c calculates luminance data from the corrected spectral characteristic and stores it in the storage device 40 inside the PC 6 (S224).

  FIG. 10B is a diagram illustrating a calculation method of luminance data. The luminance data S (pls) is a value obtained by integrating the corrected spectral characteristic LNS (n) in the entire wavelength region. That is, in FIG. 10B, it is expressed as the area inside the curve LNS (n). Here, pls indicates the number of pulses given to the aperture motor 16 when the aperture is reduced from the open state. Accordingly, S (0) represents the luminance in the fully open state.

  If the diaphragm 20 is not yet fully squeezed (No in S225), the diaphragm motor 16 is driven by a predetermined amount, and the process from Step S222 to Step S224 is repeatedly executed with the diaphragm 20 changed. (C) of FIG. 10 is a figure which shows the luminance data after changing an aperture_diaphragm | restriction. It is shown that the luminance data S (pls) is decreased by changing the aperture.

  If the aperture 20 has already been reduced to the maximum position (S225 Yes), the aperture motor 16 is driven by a predetermined amount to open the aperture 20 to the reference position (S227).

  Next, the effective aperture value calculation unit 6d is activated, calculates an effective aperture value based on the luminance data, and creates a correspondence table between the number of driving pulses of the aperture motor 16 and the effective aperture value (S228).

The effective aperture value is expressed by equation (3) using the above-described luminance data.
Effective aperture value = AV0−log ₂ {S (pls) / S (0)} (3)
Here, AV0 is an aperture value when the aperture is opened, and a design value is adopted.

  Note that equation (3) can also be expressed by equation (4) using the narrowing position P, which is a superordinate concept, instead of the number of drive pulses pls.

Effective aperture value = AV0−log ₂ {S (P) / S (0)} Expression (4)
AV0: Open aperture value in the design of the test lens S (P): Luminance data at the aperture position P S (0): Luminance data at the aperture position FIG. 11 shows the correspondence between the number of driving pulses of the aperture motor 16 and the effective aperture value. It is a figure which shows a table | surface. In the “change in aperture value” column of FIG. 11, a value obtained by calculating log ₂ {S (pls) / S (0)} of the second term on the right side of the equation (3) is described. AV0 adopts a design value (= 5) of a lens with F = 5.6.

  Then, in the PC 6, the storage control unit 6e is activated to transmit the number of driving pulses of the aperture motor 16 and the effective aperture value calculated correspondingly to the microprocessor 25 to be stored in the internal flash ROM 25a (S229). .

  Through the above operation, after storing information on the spectral characteristics and the lens characteristics of the effective aperture value in the lens, the operator indicates whether or not each value is within the standard value on a display device (not shown) of the PC 6. Judgment is made based on the displayed values (T105, T106). If any of the values deviates from the standard value (T105, T106 No), the lens is returned to the assembly process (T107). If both are within the standard values (T105, T106 Yes), the lens is sent to the next adjustment step (T108).

  According to this embodiment, it is possible to automate the measurement work of lens characteristics and the work of incorporating the lens characteristic information into the lens, so that the burden on the operator can be reduced and the work efficiency can be increased.

  In addition, since these lens characteristics can be measured as a series of operations, the efficiency of the camera assembly line can be improved.

  Note that the present invention is not limited to the above-described embodiment as it is, and can be embodied by modifying the constituent elements without departing from the scope of the invention in the implementation stage. Further, various inventions can be formed by appropriately combining a plurality of constituent elements disclosed in the embodiment. For example, some components may be deleted from all the components shown in the embodiment. Furthermore, you may combine suitably the component covering different embodiment.

The block diagram which shows the structure of an electronic camera. The figure which shows the structure of the lens measuring machine which concerns on embodiment of this invention. The figure which shows the structure of PC. The flowchart which shows the general | schematic procedure of the measurement / incorporation operation | work of a lens characteristic using a lens measuring machine. The flowchart which shows the measurement / incorporation procedure of the lens characteristic of PC. The flowchart which shows the measurement / incorporation procedure of the lens characteristic of PC. The figure which shows a spectral characteristic. The figure which shows the spectral transmittance characteristic of an imaging lens. The figure which shows a spectral transmittance table. The figure explaining calculation of luminance data. The figure which shows the correspondence table of the drive pulse number of an aperture motor, and an effective aperture value.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Lens holding jig, 2 ... Luminance box, 3 ... Spectroscope, 3e ... CCD run sensor, 6 ... PC, 6b ... Spectral transmittance detection part, 6c ... Luminance calculation part, 6d ... Effective aperture value calculation part, 6e ... Memory Control unit, 11 ... photographing lens, 12 ... lens motor, 16 ... aperture motor, 20 ... aperture, 25 ... microcomputer, 25a ... Flash ROM, 43 ... photometric circuit.

Claims (3)

A mount for mounting the test lens;
A light source that emits a measuring beam;
Photometric means for measuring the light intensity for each wavelength of the measurement light beam incident through the lens to be mounted mounted on the mount and the measurement light beam incident without passing through the test lens. When,
Spectral transmittance detecting means for detecting the spectral transmittance of the test lens based on the output data of the photometric means in each case,
Luminance calculation means for calculating luminance data from the output of the photometry means and spectral characteristics of other photometry means provided in the camera body to which the lens to be examined is mounted;
An effective aperture that moves an aperture provided in the lens to be tested mounted on the mount to a plurality of positions including an open position and detects an effective aperture value based on the luminance data at each position. A value detection means;
Memory for storing data based on the output of the spectral transmittance detecting means and correspondence data between the aperture position and the effective aperture value based on the output of the effective aperture value detecting means in a storage means provided in the lens to be examined And a control means.   The spectral transmittance detecting means calculates a ratio between spectral data of the measurement light beam incident through the test lens and spectral data of the measurement light beam incident without passing through the test lens, and a result of the ratio calculation. The lens measuring machine according to claim 1, wherein the spectral transmittance is outputted by performing a normalization operation on the lens. The lens measuring machine according to claim 1, wherein the effective aperture value detecting means calculates the effective aperture value (AVR) by the following equation.
AVR = AV0−log ₂ {S (P) / S (0)}
AV0: Open aperture value in the design of the test lens S (P): Luminance data at the aperture position P S (0): Luminance data at the open position

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